I wanted a good portrait lens at an affordable price. I find this lens to be a real pleasure to use. The bokeh is soooooo dreamy...I love it! It's tricky to use at 1.8 and it's easy to get overly soft captures at 1.8.

IMHO, it just doesn't justify the price difference from the nifty-fifty

Don't get me wrong, this lens IS better than the 1.8. The build quality is better and the AF is faster and quieter (USM), but when it comes down to side-by-side image comparisons, there's only a small margin of "betterness" with the 1.4 IMHO.

Wonderful lens. Built like a tank and performs like a gem! I don't think this lens carries Canon's top autofocus abilities and therefore it is actually a bit slower on AF than the 50mm 1.4 usm. Give this lens a chance if you struggle at first using it, it takes practice.

No hood which is highly recommended. Vignetting and barrel distortion.

Really a very nice lens for APS-C bodies such as the XTi/400D, 30/40D, and the upcoming XSi/450D.

The Vignetting and barrel distortion is easily corrected in post-processing. Really a nice sharp and fun lens to use. Only drawbacks are that it doesn't include a lens hood and it's somewhat slow on aperture sizes and thus is not good in low light w/o a tripod.

Sharp, good color, great for longer reach macro, and built like a tank!

Cons:

Cost and weight.

Built better than the Canon 100mm f/2.8 macro USM, every bit as good as the 100mm macro. Very sharp and good colors. This lens is a tank, but you will get more reach from it. Great lens, no issues here!

A little degree of CA (purple fringing) present and a little slow on the AF side.

This is the widest rectilinear wide-angle lens I would ever recommend. For me, it's exactly what I was looking for in a wide-angle. Expect edge-softness at 10mm and probably more so on a full-frame sensor.